Quick start tutorial

Let's assume you maintain a program named foo which has a man page man/foo.1 written in English (the bridge language in most open-source projects, but po4a can be used from or to any language). Some times ago, someone provided a German translation named man/foo.de.1 and disappeared. This is a problem because you just got a bug report saying that your documentation contains a gravely misleading information that must be fixed in all languages, but you don't speak German so you can only modify the original, not the translation. Now, another contributor wants to contribute a translation to Japanese, a language that you don't master either.

It is time to convert your documentation to po4a to solve your documentation maintenance nightmares. You want to update the doc when needed, you want to ease the work of your fellow translators, and you want to ensure that your users never see any outdated and thus misleading documentation.

The conversion includes two steps: setup the po4a infrastructure, and convert the previous German translation to salvage the previous work. This latter part is done using po4a-gettextize, as follows. As detailed in the documentation of po4a-gettextize(1), this process rarely fully automatic, but once it's done, the de.po file containing the German translation can be integrated in your po4a workflow.

  po4a-gettextize --format man --master foo.1 --localized foo.de.1 --po de.po

Let's now configure po4a. With the appropriate file layout, your configuration file could be as simple as this:

 [po_directory] man/po4a/
 [type: man] man/foo.1 $lang:man/translated/foo.$lang.1

It specifies that all PO files (containing the work of the translators) are the man/po4a/ directory, and that you have only one master file, man/foo.1. If you had several master files, you would have several lines similar to the second one. Each such line also specify where to write the corresponding translation files. Here, the German translation of man/foo.1 is in man/translated/foo.de.1.

The last thing we need to complete the configuration of po4a is a POT file containing the template material that should be used to start a new translation. Simply create an empty file with the .pot extension in the specified po_directory (e.g. man/po4a/foo.pot), and po4a will fill it with the expected content.

Here is a recap of the files in this setup:

  ├── man/
  │   ├── foo.1        <- The original man page, in English.
  │   ├── po4a/
  │   │   ├── de.po    <- The German PO translation, from gettextization.
  │   │   └── foo.pot  <- The POT template of future translations (empty at first)
  │   └── translated/  <- Directory where the translations will be created
  └── po4a.cfg         <- The configuration file.

Once setup, executing po4a will parse your documentation, update the POT template file, use it to update the PO translation files, and use them to update the documentation translation files. All in one command:

        po4a --verbose po4a.cfg

This it. po4a is now fully configured. Once you've fixed your error in man/foo.1, the offending paragraph in the German translation will be replaced by the fixed text in English. Mixing languages is not optimal, but it's the only way to remove errors in translations that you don't even understand, and ensure that the content presented to the users is never misleading. Updating the German translation is also much easier in the corresponding PO file, so the language mix-up may not last long. Finally, when the Japanese translator gives you a jp.po translated file, just drop it in man/po4a/po/. A translated page will appear as man/translated/foo.jp.1 (provided that enough content is translated) when you run po4a again.

Options modifying the POT header

--porefs type

Specify the reference format. Argument type can be one of never to not produce any reference, file to only specify the file without the line number, counter to replace line number by an increasing counter, and full to include complete references (default: full).

--wrap-po no|newlines|number (default: 76)

Specify how the po file should be wrapped. This gives the choice between either files that are nicely wrapped but could lead to git conflicts, or files that are easier to handle automatically, but harder to read for humans.

Historically, the gettext suite has reformatted the po files at the 77th column for cosmetics. This option specifies the behavior of po4a. If set to a numerical value, po4a will wrap the po file after this column and after newlines in the content. If set to newlines, po4a will only split the msgid and msgstr after newlines in the content. If set to no, po4a will not wrap the po file at all. The reference comments are always wrapped by the gettext tools that we use internally.

Note that this option has no impact on how the msgid and msgstr are wrapped, i.e. on how newlines are added to the content of these strings.

--master-language

Language of the source files containing the documents to translate. Note that all master documents must use the same language.

--msgid-bugs-address email@address

Set the report address for msgid bugs. By default, the created POT files have no Report-Msgid-Bugs-To fields.

--copyright-holder string

Set the copyright holder in the POT header. The default value is "Free Software Foundation, Inc."

--package-name string

Set the package name for the POT header. The default is "PACKAGE".

--package-version string

Set the package version for the POT header. The default is "VERSION".

Options to modify the PO files

--msgmerge-opt options

Extra options for msgmerge(1).

Note: $lang will be extended to the current language.

--no-previous

This option removes --previous from the options passed to msgmerge. This is necessary to support versions of gettext earlier than 0.16.

--previous

This option adds --previous to the options passed to msgmerge. It requires gettext 0.16 or later, and is activated by default.

Finding the PO and POT files

The simplest solution is to explicitly give the path to POT and PO files, as follows:

 [po4a_paths] man/po/project.pot de:man/po/de.po fr:man/po/fr.po

This specifies the path to the POT file first, and then the paths to the German and French PO files.

The same information can be written as follows to reduce the risk of copy/paste errors:

 [po4a_langs] fr de
 [po4a_paths] man/po/project.pot $lang:man/po/$lang.po

The $lang component is automatically expanded using the provided languages list, reducing the risk of copy/paste error when a new language is added.

You can further compact the same information by only providing the path to the directory containing your translation project, as follows.

 [po_directory] man/po/

The provided directory must contain a set of PO files, each named XX.po with "XX" the ISO 639-1 of the language used in this file. The directory must also contain a single POT file, with the ".pot" file extension. For the first run, this file can be empty but it must exist (po4a cannot guess the name to use before the extension).

Note that you must choose only one between "po_directory" and "po4a_paths". The first one ("po_directory") is more compact, further reduces the risk of copy/paste error, but forces you to use the expected project structure and file names. The second one ("po4a_paths"), is more explicit, probably more readable, and advised when you setup your first project with po4a.

Centralized or split PO files?

By default, po4a produces one single PO file per target language, containing the whole content of your translation project. As your project grows, the size of these files may become problematic. When using weblate, it is possible to specify priorities for each translation segment (i.e., msgid) so that the important ones get translated first. Still, some translation teams prefer to split the content in several files.

To have one PO file per master file, you simply have to use the string $master in the name of your PO files on the "[po4a_paths]" line, as follows.

 [po4a_paths] doc/$master/$master.pot $lang:doc/$master/$lang.po

With this line, po4a will produce separate POT and PO files for each document to translate. For example, if you have 3 documents and 5 languages, this will result in 3 POT files and 15 PO files. These files are named as specified on the "po4a_paths" template, with $master substituted to the basename of each document to translate. In case of name conflict, you can specify the POT file to use as follows, with the "pot=" parameter.

This feature can also be used to group several translated files into the same POT file. The following example only produces 2 POT files: l10n/po/foo.pot (containing the material from foo/gui.xml) and l10n/po/bar.pot (containing the material from both bar/gui.xml and bar/cli.xml).

 [po4a_langs] de fr ja
 [po4a_paths] l10n/po/$master.pot $lang:l10n/po/$master.$lang.po
 [type: xml] foo/gui.xml $lang:foo/gui.$lang.xml pot=foo
 [type: xml] bar/gui.xml $lang:bar/gui.$lang.xml pot=bar
 [type: xml] bar/cli.xml $lang:bar/cli.$lang.xml pot=bar

In split mode, po4a builds a temporary compendium during the PO update, to share the translations between all the PO files. If two PO files have different translations for the same string, po4a will mark this string as fuzzy and will submit both translations in all the PO files containing this string. When unfuzzied by the translator, the translation is automatically used in every PO files.

Specifying the documents to translate

You must also list the documents that should be translated. For each master file, you must specify the format parser to use, the location of the translated document to produce, and optionally some configuration. Here is an example:

 [type: sgml] doc/my_stuff.sgml fr:doc/fr/mon_truc.sgml \
              de:doc/de/mein_kram.sgml
 [type: man] script fr:doc/fr/script.1 de:doc/de/script.1
 [type: docbook] doc/script.xml fr:doc/fr/script.xml \
             de:doc/de/script.xml

But again, these complex lines are difficult to read and modify, e.g. when adding a new language. It is much simpler to reorganize things using the $lang template as follows:

 [type: sgml]    doc/my_stuff.sgml $lang:doc/$lang/my_stuff.sgml
 [type: man]     script.1          $lang:po/$lang/script.1
 [type: docbook] doc/script.xml    $lang:doc/$lang/script.xml

Specifying options

There is two types of options: po4a options are default values to the po4a command line options while format options are used to change the behavior of the format parsers. As a po4a options, you could for example specify in your configuration file that the default value of the --keep command line parameter is 50% instead of 80%. Format options are documented on the specific page of each parsing module, e.g. Locale::Po4a::Xml(3pm). You could for example pass nostrip to the XML parser to not strip the spaces around the extracted strings.

You can pass these options for a specific master file, or even for a specific translation of that file, using "opt:" and "opt_XX:" for the "XX" language. In the following example, the nostrip option is passed to the XML parser (for all languages), while the threshold will be reduced to 0% for the French translation (that is thus always kept).

 [type:xml] toto.xml $lang:toto.$lang.xml opt:"-o nostrip" opt_fr:"--keep 0"

In any case, these configuration chunks must be located at the end of the line. The declaration of files must come first, then the addendum if any (see below), and then only the options. The grouping of configuration chunks is not very important, since elements are internally concatenated as strings. The following examples are all equivalent:

  [type:xml] toto.xml $lang:toto.$lang.xml opt:"--keep 20" opt:"-o nostrip" opt_fr:"--keep 0"
  [type:xml] toto.xml $lang:toto.$lang.xml opt:"--keep 20 -o nostrip" opt_fr:"--keep 0"
  [type:xml] toto.xml $lang:toto.$lang.xml opt:--keep opt:20 opt:-o opt:nostrip opt_fr:--keep opt_fr:0

Note that language specific options are not used when building the POT file. It is for example impossible to pass nostrip to the parser only when building the French translation, because the same POT file is used to update every languages. So the only options that can be language-specific are the ones that are used when producing the translation, as the "--keep" option.

Configuration aliases

To pass the same options to several files, the best is to define a type alias as follows. In the next example, "--keep 0" is passed to every Italian translation using this "test" type, that is an extension of the "man" type.

  [po4a_alias:test] man opt_it:"--keep 0"
  [type: test] man/page.1 $lang:man/$lang/page.1

You can also extend an existing type reusing the same name for the alias as follows. This is not interpreted as as an erroneous recursive definition.

  [po4a_alias:man] man opt_it:"--keep 0"
  [type: man] man/page.1 $lang:man/$lang/page.1

Global default options

You can also use "[options]" lines to define options that must be used for all files, regardless of their type.

  [options] --keep 20 --option nostrip

As with the command line options, you can abbreviate the parameters passed in the configuration file:

  [options] -k 20 -o nostrip

Option priorities

The options of every sources are concatenated, ensuring that the default values can easily be overridden by more specific options. The order is as follows:

• "[options]" lines provide default values that can be overridden by any other source.
• Type aliases are then used. Language specific settings override the ones applicable to all languages.
• Settings that are specific to a given master file override both the default ones and the ones coming from the type alias. In this case also, language specific settings override the global ones.
• Finally, parameters provided on the po4a command line override any settings from the configuration file.

Example

Here is an example showing how to quote the spaces and quotes:

 [po_directory] man/po/
 
 [options] --master-charset UTF-8
 
 [po4a_alias:man] man opt:"-o \"mdoc=NAME,SEE ALSO\""
 [type:man] t-05-config/test02_man.1 $lang:tmp/test02_man.$lang.1 \
            opt:"-k 75" opt_it:"-L UTF-8" opt_fr:--verbose

Addendum: Adding extra content in the translation

If you want to add an extra section to the translation, for example to give credit to the translator, then you need to define an addendum to the line defining your master file. Please refer to the page po4a(7) for more details on the syntax of addendum files.

 [type: pod] script fr:doc/fr/script.1 \
             add_fr:doc/l10n/script.fr.add

You can also use language templates as follow:

 [type: pod] script $lang:doc/$lang/script.1 \
             add_$lang:doc/l10n/script.$lang.add

If an addendum fails to apply, the translation is discarded.

Modifiers for the addendum declaration

Addendum modifiers can simplify the configuration file in the case where not all languages provide an addendum, or when the list of addenda changes from one language to the other. The modifier is a single char located before the file name.

?

Include addendum_path if this file does exist, otherwise do nothing.

@

addendum_path is not a regular addendum but a file containing a list of addenda, one by line. Each addendum may be preceded by modifiers.

!

addendum_path is discarded, it is not loaded and will not be loaded by any further addendum specification.

The following includes an addendum in any language, but if only it exists. No error is reported if the addendum does not exist.

 [type: pod] script $lang:doc/$lang/script.1  add_$lang:?doc/l10n/script.$lang.add

The following includes a list of addendum for every language:

 [type: pod] script $lang:doc/$lang/script.1  add_$lang:@doc/l10n/script.$lang.add

Filtering the translated strings

Sometimes, you want to hide some strings from the translation process. To that extend, you can give a "pot_in" parameter to your master file to specify the name of the file to use instead of the real master when building the POT file. Here is an example:

  [type:docbook] book.xml          \
          pot_in:book-filtered.xml \
          $lang:book.$lang.xml

With this setting, the strings to translate will be extracted from the book-filtered.xml (that must be produced before calling po4a) while the translated files will be built from book.xml. As a result, any string that is part of book.xml but not in book-filtered.xml will not be included in the PO files, preventing the translators from providing a translation for them. So these strings will be left unmodified when producing the translated documents. This naturally decreases the level of translation, so you may need the "--keep" option to ensure that the document is produced anyway.